Thursday, October 28, 2010

"Love" Birds: Mated for Life but Bound to Cheat?

James Owenfor National Geographic News

February 14, 2003

Oft have I heard both youth and virgin sayBirds choose their
mates, and couples too, this day;But by their flight I never can
divine,When I shall couple with my ValentineRobert
Herrick, 17th century English poet

The mating game seems so simple for birds. They court, pair up, make a cozy nest, and devote themselves to raising a familyeach partner caring for the other as they share the task of parenthood. If only we could be like them.

The English priest and naturalist F.O. Morris, who wrote A History of British Birds in the mid-1800s , had the same message for his parishioners during a Sunday sermon. His perfect role model was the dunnock, a perky little bird of the English countryside.

Morris described it as "unobtrusive, quiet and retiring, without being shy, humble and homely in its deportment and habits, sober and unpretending in its dress." In short, the bird set an example in plain, decent living that his congregation would do well to follow.

Over 130 years later, the dunnock was described in a rather different way by Nick Davies, a British behavioral ecologist.

"A pair of dunnocks had been feeding together, hopping peacefully towards a bush. Reaching it, the male proceeded to one side, the female to the other. Once out of the male's field of vision, the female instantly flew into the nearby undergrowth, where she copulated with a different male dunnock who had been hidden there. Immediately afterward she rejoined her mate, all the while acting as though nothing had happened."

In recent decades the sex lives of birds have become a lot less worthy and a lot more interesting. In fact, they are proving every bit as complex and messy as our own.

DNA analysis in the 1980s revealed that male partners of many nesting bird pairs often reared chicks that weren't their own. Females, it was shown, are not terribly faithful.

This came as a surprise. Birds are much more likely to pair-bondform a partnership that extends beyond copulationthan other animals. Social monogamy is thought to exist in 90 percent of bird species. Only five percent of mammals are thought to be socially monogamous, including gibbons, jackals, and tamarins.

"Extramarital Affairs"

For some bird species pair-bonding lasts a lifetime. The Bewick's swan and the waved albatross are two examples. But for others all the "extramarital affairs" clearly take their toll. House martins and greater flamingos are the Elizabeth Taylors of the bird world, with 100 percent of pairings resulting in "divorce."